Electronic apparatus including a cooling unit for cooling a heat generating component

ABSTRACT

An electronic apparatus comprises a housing for accommodating a heat generating component and a display unit supported by the housing. A heat receiving head thermally connected to the heat generating component is accommodated inside the housing. A heat radiator is disposed in the display unit. A heat receiving head and the heat radiator are connected to each other through a circulating path for circulating cooling medium. The circulating path is provided with an intermediate cooling unit. Before cooling medium heated by heat transfer by the heat receiving head reaches the heat radiator, the intermediate cooling unit forces cooling medium to be cooled.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2000-287691, filed Sep.21, 2000, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a cooling unit for forcing aheat generating component like a semiconductor package to be cooled withliquid-like cooling medium and an electronic apparatus provided with thecooling unit, such as a portable computer.

[0004] 2. Description of the Related Art

[0005] An electronic apparatus like a portable computer has a microprocessing unit (MPU) for processing multimedia information such ascharacters, voices and animation. This MPU tends to increase generationof heat during its operation accompanied by currently increasedprocessing speed and multiple functions. Thus, in order to ensure astable operation of the MPU, it is necessary to intensify heat radiationperformance of this MPU.

[0006] Conventionally, a portable computer loaded with a MPU generatinga large amount of heat is equipped with an air-cooling type cooling unitfor forcing the MPU to be cooled. This cooling unit has a heat sinkthermally connected to the MPU and an electric fan for supplying coolingair to this heat sink.

[0007] In this cooling unit, heat from the MPU is transmitted to theheat sink and then discharged out of the computer through a flow ofcooling air. Therefore, because according to the conventional coolingmethod, cooling air serves as a cooling medium for depriving the MPU ofheat, the cooling performance of the MPU mostly depends on air feedingperformance of the electric fan. If the feeding amount of cooling air isincreased to aim at intensifying cooling performance of the MPU, therotation amount of the electric fan is increased, so that there isproduced such a problem that a large noise may be produced.Additionally, because in the portable computer, a housing forincorporating the MPU and electric fan is designed so thin in a compactbody, it is difficult to secure a space for accommodating a largeelectric fan having an excellent air feeding performance and an idealair feeding path inside the housing.

[0008] In near future, it is expected that the processing speed of theMPU for the portable computer will be further accelerated and the MPUwill become multifunctional, and accompanied by this trend, the heatgeneration of the MPU increases tremendously. Thus, the conventionalforced air-cooling system has a fear that the cooling capacity for theMPU becomes short or reaches its limit.

[0009] As a means for improving this, for example, Jpn. Pat. Appln.KOKAI Publication No. 7-142886 has disclosed so-called liquid coolingsystem employing liquid having a higher specific heat than air as heattransferring medium.

[0010] According to this new cooling system, a heat receiving headerconnected to the MPU thermally is disposed inside the housing and a heatradiating header is disposed inside the display housing supported bythis housing. The heat receiving header and the heat radiating headerare connected to each other through a circulating pipe in whichliquid-like cooling medium flows.

[0011] Because according to this cooling system, cooling mediumcirculates between the heat receiving header and the heat radiatingheader, heat from the MPU is transmitted to the heat receiving headerand after that, transferred to the heat radiating header via the coolingmedium. Heat transferred to the heat radiating header is discharged tothe atmosphere by diffusion by heat conduction to the display housing.For the reason, the heat radiating header is connected thermally to thedisplay housing and the display housing is composed of metallic materialhaving excellent heat conductivity.

[0012] Therefore, such liquid cooling system is capable of transferringheat of the MPU more effectively than the conventional forced aircooling system, thereby raising the cooling performance of the MPU.

[0013] Meanwhile, heat of the MPU transferred from the heat radiatingheader to the display housing is discharged to the atmosphere from thesurface of the display housing through natural convection and heatradiation. Thus, as the amount of heat transferred to the displayhousing increases, the surface temperature of the display housing israised. As a result, if user happens to touch the surface of the displayhousing when opening/closing the display housing or carrying thecomputer, he or she may feel discomfort or heat.

[0014] Further, according to the liquid cooling system, a heat radiatingheader inside the display housing is connected to a heat receivingheader inside the housing through a circulating pipe. Thus, if anecessity of removing this display housing from the housing occurs tocarry out maintenance on the interior of the display housing, the heatreceiving header thermally connected to the MPU needs to be removed fromthe housing temporarily.

[0015] However, disassembly of the periphery of such a precision MPU notonly leads to damage of the MPU but also may make inappropriate thepositional relationship between the heat receiving header and the MPUupon installation of the heat receiving header. Thus, this isunfavorable in terms of maintaining reliability of thermal connectionbetween the MPU and the heat receiving header.

[0016] If the MPU is loaded on a place difficult to access like a rearface of a circuit board, a troublesome work of disassembling the housingand taking out the circuit board is required. This work can be said tobe inappropriate in viewpoint of operation efficiency and therefore,there is a room for improvement at this point.

BRIEF SUMMARY OF THE INVENTION

[0017] A first object of the present invention is to provide a coolingunit and an electronic apparatus capable of preventing a rise intemperature of the surface of a display unit.

[0018] A second object of the present invention is to provide anelectronic apparatus, which allows a second housing to be removed from afirst housing without releasing thermal connection between a heatreceiving portion and a heat generating component and which can bedisassembled/reassembled easily and maintain reliability of heatconduction favorably.

[0019] In order to achieve the above-described first object, accordingto a first aspect of the present invention, there is provided a coolingunit for use in an electronic apparatus having a computer main bodycontaining a heat generating component and a display unit supported bythe computer main body, the cooling unit comprising: a heat receivingportion thermally connected to the heat generating component andaccommodated in the computer main body; a heat exchanging portioninstalled on the display unit; circulating means for circulating coolingmedium between the heat receiving portion and the heat exchangingportion, the circulating means having a pipe line for introducingcooling medium heated by the heat receiving portion to the heatexchanging portion; and intermediate cooling means installed in the pipeline, the intermediate cooling means forcing the heated cooling mediumflowing from the heat receiving portion to the heat exchanging portionto be cooled.

[0020] Further, in order to achieve the above-described first object,according to a second aspect of the present invention, there is providedan electronic apparatus comprising: a housing containing a heatgenerating component; a display unit supported by the housing; a heatreceiving portion accommodated in the housing and thermally connected tothe heat generating component; a heat exchanging portion installed onthe display unit; circulating means for circulating cooling mediumbetween the heat receiving portion and the heat exchanging portion, thecirculating means being disposed throughout the housing and the displayunit and having a pipe line for introducing cooling medium heated by theheat receiving portion to the heat exchanging portion; and intermediatecooling means installed in the pipe line of the circulating means, theintermediate cooling means forcing the heated cooling medium flowingfrom the heat receiving portion to the heat exchanging portion to becooled.

[0021] With such a structure, heat from the heat generating component istransferred to the cooling medium by means of the heat receivingportion. This heat is transmitted to the heat exchanging portion througha flow of the cooling medium. The cooling medium cooled by heat exchangeby means of the heat exchanging portion is returned to the heatreceiving portion and receives heat from the heat generating componentagain. By repeating such a cycle, heat from the heat generatingcomponent is transmitted to the display unit effectively and dischargedto the atmosphere.

[0022] The cooling medium heated through heat conduction from the heatreceiving portion is cooled via the intermediate cooling means before itreaches the heat exchanging portion. Thus, the temperature of thecooling medium introduced by the heat exchanging portion can be lowered.Thus, the rise in temperature of the surface of the display unit can besuppressed despite discharging heat from the heat generating componentfrom the display unit, so that a bad influence upon user using theelectronic apparatus can be reduced to such a level having no problem.

[0023] In order to achieve the above-described second object, accordingto a third aspect of the present invention, there is provided anelectronic apparatus comprising: a first housing containing a heatgenerating component; a second housing, the second housing beingjournaled detachably on a rear end of the first housing through a hingedevice having a hinge shaft extending in the width direction of thefirst housing and having a rear face which is directed backward of thefirst housing when the second housing is rotated to a posture in whichit stands up from the rear end of the first housing; a heat receivingportion accommodated inside the first housing and thermally connected tothe heat generating component; a heat exchanging portion installed onthe second housing, the heat exchanging portion being capable of beingtaken out of the rear face; and circulating means for circulating thecooling medium between the heat receiving portion and the heatexchanging portion, the circulating means comprising a first pipe linefor introducing cooling medium heated by the heat receiving portion tothe heat exchanging portion and a second pipe line for introducingcooling medium cooled by heat exchange by means of the heat exchangingportion to the heat receiving portion, the first and second pipe linesbeing disposed throughout the inside of the first housing and the insideof the second housing via backward of the hinge shaft, the rear face ofthe second housing having at least an opening portion at a positioncorresponding to the first and second pipe lines, the opening portionbeing covered with a removable lid.

[0024] With such a structure, heat from the heat generating component istransferred to the cooling medium by means of the heat receivingportion. This heat is transferred to the heat exchanging portion throughthe cooling medium flowing through the first pipe line. The coolingmedium cooled by heat exchange by the heat exchanging portion isreturned to the heat receiving portion through the second pipe line andreceives heat from the heat generating component again. By repeatingsuch a cycle, heat from the heat generating component is transmittedeffectively to the second housing and discharged thereof to theatmosphere.

[0025] In order to remove the second housing from the first housing,first, the lid covering the opening portion of the second housing isremoved so as to expose the first and second pipe lines introduced tothe interior of the second housing through the opening portion.Subsequently, the heat exchanging portion is taken out in the directionof the rear face of the second housing and the first and second pipelines continuous to this heat exchanging portion are taken out of theopening portion. Consequently, with the first and second pipe linesconnected to the heat exchanging portion, this heat exchanging portioncan be taken out of the second housing. Finally, the hinge device isremoved from the first housing so as to separate the second housing fromthe first housing.

[0026] In order to install the second housing onto the first housing,the second housing is installed onto the first housing through the hingedevice. After that, the heat exchanging portion is installed on thesecond housing in the direction of the rear face of the second housing.Next, the first and second pipe lines continuous to the heat exchangingportion are inserted into the second housing through the opening portionand then this opening portion is covered with the lid. As a result, thefirst housing and the second housing are connected to each other and theinstallation of the heat exchanging portion onto the second housing iscompleted.

[0027] Consequently, when removing the second housing from the firsthousing, it is not necessary to release thermal connection between theheat receiving portion and the heat generating component. Thus, atroublesome work of disassembling or reassembling portions correspondingto the heat generating component and heat receiving portion is notrequired, so that the removal of the second housing is facilitated.Further, no unreasonable force is applied to the heat generatingcomponent or the positional relationship between the heat generatingcomponent and the heat receiving portion is not changed, thereby makingit possible to maintain reliability of thermal connection between theboth.

[0028] In order to achieve the above-described second object, accordingto a fourth aspect of the present invention, there is provided anelectronic apparatus comprising: a housing accommodating a heatgenerating component and being capable of being opened upward; a displayunit supported by the housing; a heat receiving portion accommodated inthe housing and thermally connected to the heat generating component; aheat exchanging portion installed on the display unit; and circulatingmeans for circulating cooling medium between the heat receiving portionand the heat exchanging portion, the circulating means comprising afirst pipe line for introducing cooling medium heated by the heatreceiving portion to the heat exchanging portion and a second pipe linefor introducing cooling medium cooled by heat exchange by means of theheat exchanging portion to the heat receiving portion, the first andsecond pipe lines being disposed throughout the inside of the housingand the inside of the display unit and being divided to upstreamportions and downstream portions inside the housing, the upstreamportions and the downstream portions being connected detachably througha joint, the joint having closing means for closing the first and secondpipe lines when the first and second pipe lines are divided to theupstream portions and the downstream portions.

[0029] With such a structure, heat from the heat generating component istransferred to cooling medium by the heat receiving portion. This heatis transmitted to the heat exchanging portion through the cooling mediumflowing through the first pipe line. Cooling medium cooled by heatexchange by means of the heat exchanging portion is returned to the heatreceiving portion through the second pipe line and receives heat fromthe heat generating component again. By repeating such a cycle, heatfrom the heat generating component is transmitted to the second housingeffectively and discharge thereof to the atmosphere.

[0030] In order to remove the second housing from the first housing, thefirst housing is opened upward so as to expose the first and second pipelines introduced to the interior of the first housing. Next, the firstand second pipe lines extending throughout the heat receiving portionand the heat exchanging portion are divided inside the first housing.Consequently, when removing the second housing having the heatexchanging portion from the first housing, the first and second pipelines make no obstacle and the thermal connection between the heatreceiving portion and the heat generating component does not have to bereleased. As a result, a troublesome work of disassembling/reassemblingportions corresponding to the heat generating component and heatreceiving portion is not required, so that the removal of the secondhousing is facilitated. Further, no unreasonable force is applied to theheat generating component or the positional relationship between theheat generating component and the heat receiving portion is not changed,so that reliability of thermal connection between the both can bemaintained.

[0031] Further, if the upstream portions and the downstream portions ofthe first and second pipe lines are separated from each other, the firstand second pipe lines are automatically closed. Therefore, no coolingmedium leaks from the first and second pipe lines and thus, no specialwork for sealing the first and second pipe lines is required.

[0032] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0033] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiment of theinvention, and together with the general description given above and thedetailed description of the embodiment given below, serve to explain theprinciples of the invention.

[0034]FIG. 1 is a perspective view of a portable computer according to afirst embodiment of the present invention;

[0035]FIG. 2 is a perspective view of a lid for covering an openingportion in a display housing according to the first embodiment of thepresent invention;

[0036]FIG. 3 is a sectional view of the portable computer having aliquid-cooling type cooling unit according to the first embodiment ofthe present invention;

[0037]FIG. 4 is a sectional view of the portable computer indicating asecond pipe line insertion path when the display unit is rotated to itsopening position in the first embodiment of the present invention;

[0038]FIG. 5 is a sectional view of the portable computer indicating ajoint structure between the computer main body and the display unitaccording to the first embodiment of the present invention;

[0039]FIG. 6 is a sectional view of the portable computer indicating thesecond pipe line insertion path when the display unit is rotated to itsclosing position in the first embodiment of the present invention;

[0040]FIG. 7 is a sectional view of the portable computer indicating astate in which the lid thereof is removed from the display housing inthe first embodiment of the present invention;

[0041]FIG. 8 is a sectional view showing a positional relationshipbetween a heat receiving head and a semiconductor package in the firstembodiment of the present invention;

[0042]FIG. 9 is a sectional view of the heat receiving head indicatingthe structure of inside of a heat transmitting case in the firstembodiment of the present invention;

[0043]FIG. 10 is a sectional view of a heat radiator for use in thefirst embodiment of the present invention;

[0044]FIG. 11 is a sectional view of an intermediate cooling unitindicating the positional relationship between a refrigerant path and acooling air path in the first embodiment of the present invention;

[0045]FIG. 12 is a flow chart showing electric fan control system of thefirst embodiment of the present invention;

[0046]FIG. 13 is a sectional view of the portable computer indicating astate in which the heat radiator is removed form the display housing inthe first embodiment of the present invention;

[0047]FIG. 14 is a perspective view of the portable computer accordingto a second embodiment of the present invention;

[0048]FIG. 15 is a perspective view of the portable computer accordingto a third embodiment of the present invention;

[0049]FIG. 16 is a sectional view of the portable computer having aliquid cooling type cooling unit according to a fourth embodiment of thepresent invention;

[0050]FIG. 17 is a perspective view of a holder for maintaining aninterval between a first pipe line and a second pipe line constant inthe fourth embodiment of the present invention;

[0051]FIG. 18A is a sectional view of a joint indicating a state inwhich a first joint portion and a second joint portion are joinedtogether in the fourth embodiment of the present invention; and

[0052]FIG. 18B is a sectional view of the joint indicating a state inwhich the first joint portion and the second joint portion are separatedfrom each other in the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0053] Hereinafter, the first embodiment of the present inventionapplied to a portable computer will be described with reference to FIGS.1 to 13.

[0054]FIGS. 1 and 3 show a portable computer 1 which is an electronicapparatus mentioned in this specification. The portable computer 1comprises a computer main body 2 and a display unit 3, which issupported by this computer main body 2.

[0055] The computer main body 2 has a first housing 4 of syntheticresin. The first housing 4 is a flat box comprising a bottom wall 4 a,an upper wall 4 b, right/left side walls 4 c, a front wall 4 d and arear wall 4 e. The first housing 4 is composed of a base 5 having thebottom wall 4 a and a top cover 6 having the upper wall 4 b. The topcover 6 is installed detachably to the base 5. Thus, by removing the topcover 6 from the base 5, the first housing 4 is opened upward.

[0056] A hallow convex portion 8 protruded upward is formed at a rearend portion of the upper wall 4 b of the first housing 4. The convexportion 8 is extended in the width direction of the first housing 4behind a keyboard 9. The convex portion 8 has display supportingportions 10 a and 10 b on both ends thereof. The display supportingportions 10 a and 10 b are constructed in the form of a dent opencontinuously forward, upward and backward of the convex portion 8. Thebottom of each of the display supporting portions 0.10 a and 10 b islocated downward of the upper wall 4 b as shown in FIG. 4.

[0057] As shown in FIGS. 3 and 4, a circuit board 11 is accommodatedinside the first housing 4. The circuit board 11 is disposed in parallelto the bottom wall 4 a of the first housing 4. A semiconductor package12 is installed at a left end portion of the top face of the circuitboard 11 as a heat generating component.

[0058] The semiconductor package 12 composes a micro processing unit(MPU), which serves as the center of the portable computer 1. As shownin FIG. 8, the semiconductor package 12 includes a rectangular basesubstrate 13 and an IC chip 14 soldered on the top face of this basesubstrate 13. The base substrate 13 is soldered to the top face of thecircuit board 11 through plural soldering balls 15. In this kind of thesemiconductor package 12, its power consumption during operation hasbeen increased accompanied by currently intensified processing speed andmultiple functions, so that heat generation from the IC chip 14 hasbecome so large that cooling of the chip is required.

[0059] As shown in FIGS. 1 and 3, the display unit 3 comprises a displayhousing 17 serving as a second housing and a liquid crystal displaypanel 18 accommodated in this display housing 17. The display housing 17is composed of, for example, synthetic resin material and constructed inthe form of a thin flat box having a front face 20 in which an openingportion 19 is formed and a rear face 21 opposing this front face 20. Theliquid crystal display panel 18 has a display screen (not shown) fordisplaying information such as characters and pictures. This displayscreen is exposed out of the display housing 17 through the openingportion 19.

[0060] The display housing 17 has a pair of leg portions 23 a and 23 bprotruded from an end portion thereof. The leg portions 23 a and 23 bare hallow and apart from each other in the width direction of thedisplay housing 17. The leg portions 23 a and 23 b are introduced to thedisplay supporting portions 10 a and 10 b in the first housing 4.

[0061] The right leg portion 23 a is supported by the first housing 4via a hinge device 24. The hinge device 24 comprises a first bracket 25,a second bracket 26 and a hinge shaft 27. As shown in FIG. 5, the firstbracket 25 is screwed to a top end of plural boss portions 28 extendedupward from the bottom wall 4 a. A rear end portion of the first bracket25 is introduced to inside of the convex portion 8 on the right side ofthe display supporting portion 10 a. As shown in FIG. 4, the secondbracket 26 is screwed to an inside face at the right end of the frontface 20 of the display housing 17. An end portion of the second bracket26 is introduced into inside of the right leg portion 23 a. The hingeshaft 27 is stretched between the rear end portion of the first bracket23 a and the end portion of the second bracket 26 such that it passesthrough a side face of the leg portion 23 a and a side face of thedisplay supporting portion 10 a. For the reason, the hinge shaft 27 isdisposed horizontally along the width direction of the first housing 4and the display housing 17.

[0062] An end portion of the hinge shaft 27 is rotatably coupled withthe rear end portion of the first bracket 25. The other end portion ofthe hinge shaft 27 is fixed to the end portion of the second bracket 26.A friction type brake mechanism (not shown) employing, for example, awave washer is built in a joint portion between the hinge shaft 27 andthe first bracket 25. This brake mechanism limits a free rotation of thehinge shaft 27.

[0063] Thus, the display unit 3 is rotatable around the hinge shaft 27.If speaking more in detail, the display unit 3 is supported on the firsthousing 4 rotatably with respect to the hinge shaft 27 from a closingposition in which the same display unit 3 is tilted down so as to coverthe key board 9 to an opening position in which it is raised so as toexpose the key board 9 and the display screen. When the display unit 3is turned to the opening position, the rear face 21 of the displayhousing 17 is directed rearward of the portable computer 1.

[0064] As shown in FIG. 3, the portable computer 1 incorporates a liquidcooling type cooling unit 30 for forcing the semiconductor package 12 tobe cooled. The cooling unit 30 comprises a heat receiving head 31 as aheat receiving portion, a heat radiator 32 as a heat exchanging portionand a circulation path 33 as circulating means.

[0065] As shown in FIGS. 8 and 9, the heat receiving head 31 isaccommodated in the first housing 4. This heat receiving head 31 has aheat transmitting case 34. The heat transmitting case 34 is composed ofmetal material having an excellent thermal conductivity like aluminumalloy. This heat transmitting case 34 is constructed in the form of athin flat box having a plane larger than the semiconductor package 12.

[0066] The heat transmitting case 34 contains plural guide walls 35inside. The guide walls 35 are disposed in parallel to each other withan interval between one and another, so that the inside of the heattransmitting case 34 is divided to plural refrigerant flow paths 36. Theheat transmitting case 34 has a refrigerant intake 37 and a refrigerantoutlet 38. The refrigerant intake 37 is located at an upstream end ofthe refrigerant flow paths 36. The refrigerant outlet 38 is located at adownstream end of the refrigerant flow paths 36.

[0067] The heat transmitting case 34 is supported on the top face of thecircuit board 11 via its four corner portions with screws 39. This heattransmitting case 34 opposes the circuit board 11 across thesemiconductor package 12. A heat transmitting sheet 40 is disposedbetween the central portion on the bottom face of the heat transmittingcase 34 and the IC chip 14 of the semiconductor package 12. The heattransmitting case 34 is pressed against the IC chip 14 through a leafspring 41 so that the heat transmitting sheet 40 is sandwiched betweenthe heat transmitting case 34 and the IC chip 14. Thus, the heattransmitting case 34 is thermally in contact with the IC chip 14 throughthe heat transmitting sheet 40.

[0068] As shown in FIGS. 3 and 4, the heat radiator 32 is accommodatedinside the display housing 17. The heat radiator 32 has the first andsecond heat radiating plates 43 a and 43 b. The first and second heatradiating plates 43 a and 43 b are composed of metal material having anexcellent thermal conductivity like for example aluminum alloy and havesubstantially the same size as the liquid crystal display panel 18.

[0069] As shown in FIG. 10, the first heat radiating plate 43 a and thesecond heat radiating plate 43 b are overlaid over each other. Thesecond heat radiating plate 43 b has a concave portion 44, which is opento a matching face with the first heat radiating plate 43 a. The concaveportion 44 is formed meanderingly on substantially entire surface of thesecond heat radiating plate 43 b. The concave portion 44 forms aradiated heat path 45 with the matching face with the first heatradiating plate 43 a. The radiated heat path 45 has a refrigerant intake46 and a refrigerant outlet 47. The refrigerant intake 46 is open to theleft leg portion 23 b inside the display housing 17. The refrigerantoutlet 47 is open to the right leg portion 23 a inside the displayhousing 17. Thus, the refrigerant intake 46 and the refrigerant outlet47 are apart from each other in the width direction of the displayhousing 17.

[0070] The aforementioned circulation path 33 has a first pipe line 50and a second pipe line 51. The first and second pipe lines 50 and 51 arecomposed of metallic pipe of, for example, stainless.

[0071] The first pipe line 50 connects the refrigerant outlet 38 of theheat receiving head 31 to the refrigerant intake 46 of the heat radiator32. The first pipe line 50 is extended toward the display supportingportion 10 b on the left inside the first housing 4. After a front endof this first pipe line 50 passes through a front face of the displaysupporting portion 10 b and a front face of the leg portion 23 b on theleft, it is introduced into the display housing 17.

[0072] The second pipe line 51 connects the refrigerant intake 37 of theheat receiving head 31 to the refrigerant outlet 47 of the heat radiator32. After the second pipe line 51 is introduced to the right side alongthe front wall 4 d inside the first housing 4, it is extended toward thedisplay supporting portion 10 a on the right. After a front end of thesecond pipe line 51 passes through a front face of the displaysupporting portion 10 a and a front face of the leg portion 23 a on theright, it is introduced to the leg portion 23 b and then introduced intothe display housing 17.

[0073] Therefore, the refrigerant flow paths 36 of the heat receivinghead 31 is connected to the radiated heat path 45 of the heat radiator32 through the first and second pipe lines 50 and 51. The refrigerantflow path 36, the radiated heat path 45 and the first/second pipe lines50 and 51 are filled with liquid-like cooling medium like water orfluorocarbon.

[0074] As shown in FIGS. 3 and 5, of the first and second pipe lines 50and 51, portions passing through the leg portions 23 a and 23 b of thedisplay housing 17 are composed of an expandable bellows pipe 52 havinga flexibility. The bellows pipes 52 are curved in the form of a circlearound the hinge shaft 27 and disposed behind this hinge shaft 27.

[0075] Thus, the bellows pipes 52 of the first and second pipe lines 50and 51 are deformable freely in a direction around the hinge shaft 27.Consequently, the first and second pipe lines 50 and 51 are deformedsmoothly following a rotation of the display unit 3 when it is rotatedfrom its closing position to its opening position, so as to absorb acurve applied to the first and second pipe lines 50 and 51 when thedisplay unit 3 is rotated.

[0076] As shown in FIG. 1, the display housing 17 has a mounting port54, which is open in the rear face 21 thereof. The mounting port 54 islocated behind the liquid crystal display panel 18 and has a sizefitting to the heat radiator 32. The first heat radiating plate 43 a ofthe heat radiator 32 has a lower edge portion adjacent the leg portions23 a and 23 b of the display housing 17 and an upper edge portionlocated on an opposite side to this lower edge portion. A pair offitting pawls 55 a and 55 b are formed on the upper edge portion of thefirst heat radiating plate 43 a. These fitting pawls 55 a and 55 b areapart from each other in the width direction of the display housing 17.

[0077] The heat radiator 32 is fit to the mounting port 54 from the rearface 21 of the display housing 17.

[0078] Consequently, the fitting pawls 55 a and 55 b of the heatradiator 32 are hooked on the opening edge portion of the mounting port54 detachably. Further, the first and second heat radiating plates 43 aand 43 b are fixed to an inside face of the display housing 17 throughtwo positions on the lower edge portion with screws 56. Thus, the heatradiator 32 is maintained such that it is in contact with the insideface of the display housing 17 so that it is thermally connected to thedisplay housing 17.

[0079] As shown in FIG. 4, an opposite surface to the second heatradiating plate 43 b of the first heat radiating plate 43 a of the heatradiator 32 is covered with protective layer 57. The protective layer 57is composed of synthetic resin having lower thermal conductivity thanthe first and second heat radiating plates 43 a and 43 b. Thisprotective layer 57 is exposed out of the display housing 17 through themounting port 54 when the heat radiator 32 is fixed to the displayhousing 17 and further, located on the same plane as the rear face 21 ofthe display housing 17.

[0080] As shown in FIG. 1, the rear face 21 of the display housing 17has a pair of opening portions 60 a and 60 b at positions correspondingto the leg portions 23 a and 23 b. The opening portions 60 a and 60 boppose the bellows pipes 52 in the first and second pipe lines 50 and51. Ends of the opening portions 60 a and 60 b reach the front ends ofthe leg portions 23 a and 23 b while the other ends of the openingportions 60 a and. 60 b are continuous to the mounting port 54. Thus,the opening portions 60 a and 60 b are large enough to take out thebellows pipes 52.

[0081] The opening portions 60 a and 60 b are covered with lids 61 ofsynthetic resin which can be removed. The lids 61 are fit to the openingportions 60 a and 60 b so that the fitting pawl 62 of each end thereofis hooked on the aforementioned heat radiator 32. The other ends of thelids 61 are fixed to the front ends of the leg portions 23 a and 23 bthrough a screw 63.

[0082] Thus, if engagement between the fitting pawl 62 and the heatradiator 32 is released by removing the screw 63 as shown in FIG. 7, thelids 61 can be removed from the display housing 17 so as to open theopening portions 60 a and 60 b. As a result, the bellows pipes 52inserted inside the leg portions 23 a and 23 b are exposed toward therear face 21 of the display housing 17 through the opening portions 60 aand 60 b.

[0083] As shown in FIGS. 3, 11, the aforementioned cooling unit 30 isequipped with an intermediate cooling unit 70 as intermediate coolingmeans. The intermediate cooling unit 70 is located halfway of the firstpipe line 50 and accommodated inside the first housing 4. Theintermediate cooling unit 70 comprises a main body 71 and an electricfan 90.

[0084] The main body 71 is composed of metallic material having anexcellent thermal conductivity like for example, aluminum alloy andscrewed to a top face on the left end portion of the circuit board 11.The main body 71 has a first concave portion 72, which is open downward.The opening end of the first concave portion 72 is sealed with a bottomplate 73. The bottom plate 73 forms a refrigerant path 74 in cooperationwith the first concave portion 72 and this refrigerant path 74 isextended in the depth direction of the first housing 4.

[0085] A pump 76 and an accumulator 77 are built in the main body 71 ofthe intermediate cooling unit 70 integratedly. A suction end of the pump76 is continuous to the refrigerant outlet 38 of the heat receiving head31 through an upstream portion of the first pipe line 50. A dischargeend of the pump 76 is continuous to the refrigerant path 74 through theaccumulator 77. This pump 76 is driven at the same time when theportable computer 1 is powered on and then pressurizes cooling mediumand supplies to the accumulator 77.

[0086] As shown in FIG. 11, the accumulator 77 has a pressureaccumulating chamber 78 for accumulating cooling medium discharged fromthe pump 76. The pressure accumulating chamber 78 is formed on a sideportion of the main body 71. Part of the peripheral wall of thispressure accumulating chamber 78 is constructed of diaphragm 79elastically deformable. If cooling medium discharged from the pump 76 issupplied to the pressure accumulating chamber 78, the diaphragm 79 iselastically deformed corresponding to a discharging pressure of thecooling medium so that the capacity of the pressure accumulating chamber78 is changed. As a result, pulsation of the cooling medium accompaniedby driving of the pump 76 is absorbed so as to adjust the dischargingpressure of the cooling medium to a constant level. This cooling mediumis supplied to the refrigerant path 74 through a communicating port 80formed in the main body 71. The refrigerant path 74 communicates with arefrigerant outlet 81 formed in the main body 71. The refrigerant outlet81 is connected to the refrigerant intake 46 of the heat radiator 32through a downstream portion of the first pipe line 50.

[0087] Therefore, cooling medium supplied to the refrigerant path 74 inthe intermediate cooling unit 70 from the pump 76 is introduced to theheat radiator 32 through the downstream portion of the first pipe line50. After this cooling medium flows through the radiated heat path 45 inthe heat radiator 32, it is introduced to the heat receiving head 31through the second pipe line 51 and from here, it is returned to anabsorption end of the pump 76 through the upperstream portion of thefirst pipe line 50. Thus, the cooling medium is forced to circulatebetween the heat receiving head 31 and the heat radiator 32.

[0088] As shown in FIG. 11, the main body 71 has a second concaveportion 83, which is open upward. The opening end of the second concaveportion 83 is sealed with a head plate 84. The head plate 84 forms acooling air path 85 in cooperation with the second concave portion 83.The cooling air path 85 adjoins the refrigerant path 74 beyond the mainbody 71 and is thermally connected to this refrigerant path 74. Thecooling air path 85 is extended in the width direction of the firsthousing 4. This cooling air path 85 has a cooling air outlet 86. Thecooling air outlet 86 opposes an exhaust port 87, which is open in theside wall 4 c on the left side of the first housing 4.

[0089] The main body 71 has a plurality of heat radiating fins 88protruded from a bottom of the second concave portion 83. These heatradiating fins 88 face the cooling air path 85 such that they areextended linearly along the cooling air path 85.

[0090] As shown in FIG. 3, the aforementioned electric fan 90 is builtin the main body 71 integratedly. The electric fan 90 is located on anopposite side to the cooling air outlet 86 of the cooling air path 85 soas to feed cooling air through the cooling air path 85. According tothis embodiment, the electric fan 90 is driven when the temperature ofthe semiconductor package 12 and the temperature of the display housing17 arrive at respective predetermined values. Thus, the heat receivinghead 31 thermally connected to the semiconductor package 12 and the heatradiator 32 are equipped with temperature sensors 91 a and 91 brespectively. The electric fan 90 is driven according to temperaturesignals from the temperature sensors 91 a and 91 b.

[0091] Next, a cooling operation of the semiconductor package 12 will bedescribed with reference to FIG. 12.

[0092] As shown in FIG. 12, power of the portable computer 1 is turnedon in step S1. Consequently, in step S2, the pump 76 of the cooling unit30 is driven so that circulation of the cooling medium between the heatreceiving head 31 and the heat radiator 32 is started.

[0093] If the IC chip 14 of the semiconductor package 12 is heatedduring an operation of the portable computer 1, heat of the IC chip 14is transmitted to the heat transmitting case 34 of the heat receivinghead 31. Heat of the IC chip 14 transmitted to the heat transmittingcase 34 is transferred to cooling medium flowing through the refrigerantflow paths 36. After heat exchange at the heat receiving head 31, heatedcooling medium is introduced to the heat radiator 32 through theupstream portion of the first pipe line 50, the refrigerant path 74 inthe intermediate cooling unit 70 and the downstream portion of the firstpipe line 50. Thus, heat of the IC chip 14 is transferred to the heatradiator 32 through a flow of the cooling medium.

[0094] The cooling medium introduced to the heat radiator 32 flowsthrough the meandering radiated heat path 45. In this flow process, heatabsorbed in the cooling medium is transmitted to the first and secondheat radiating plates 43 a and 43 b. Part of heat transmitted to thefirst and second heat radiating plates 43 a and 43 b is diffused by heattransfer to the display housing 17 so that it is discharged into theatmosphere from the surface of the display housing 17.

[0095] The protective layer 57 covering the first heat radiating plate43 a is exposed out of the display housing 17 through the mounting port54 in the rear face 21 of the display housing 17. Therefore, most ofheat transmitted to the first heat radiating plate 43 a is dischargedinto the atmosphere from the surface of the protective layer 57.

[0096] Cooling medium cooled by heat exchange by means of the heatradiator 32 is returned to the absorbing end of the pump 76 through thesecond pipe line 52. After this cooling medium is pressurized by thepump 76, it is supplied to the refrigerant flow paths 36 of the heatreceiving head 31 through the accumulator 77.

[0097] While the portable computer 1 remains powered on, thetemperatures of the semiconductor package 12 and the display housing 17are monitored by the, temperature sensors 91 a and 91 b. Thus, as longas the portable computer 1 is powered on, in step S3, the temperature ofthe semiconductor package 12 is being checked. When the temperature ofthis semiconductor package 12 reaches a predetermined level, theprocessing proceeds to step S4, in which the electric fan 90 of theintermediate cooling unit 70 is started.

[0098] If the electric fan 90 is driven, air inside the first housing 4is turned to cooling air and then fed to the cooling air path 85.Because the cooling air path 85 is thermally connected to therefrigerant path 74, part of heat in the cooling medium flowing throughthis refrigerant path 74 is taken away by flow of cooling air flowingthrough the cooling air path 85 and discharged out of the first housing4 through the exhaust port 87. Thus, the cooling medium heated by theheat receiving head 31 is cooled before it reaches the heat radiator 32,thereby the temperature of the cooling medium fed to the heat radiator32 being kept low.

[0099] Unless the temperature of the semiconductor package 12 checked instep S3 reaches the predetermined value, the processing proceeds to stepS5, in which the temperature of the display housing 17 is checked.

[0100] Because the pump 76 of the intermediate cooling unit 70 continuesto be driven as long as the portable computer 1 remains powered on, thecooling medium continues to transfer heat of the semiconductor package12 to the display housing 17. Thus, even if the temperature of thesemiconductor package 12 does not reach the predetermined value, whenthe temperature of the display housing 17 reaches the predeterminedvalue, the processing proceeds to step S4, in which the electric fan 90is started.

[0101] Consequently, part of heat in the cooling medium flowing throughthe refrigerant path 74 is taken away by a flow of cooling air flowingthrough the cooling air path 85. As a result, the temperature of coolingmedium fed to the heat radiator 32 drops, so that the amount of heattransferred from the heat radiator 32 to the display housing 17decreases.

[0102] After the driving of the electric fan 90 is started also, thetemperatures of the semiconductor package 12 and the display housing 17continue to be checked in steps S6, S7. Here, if it is determined thatthe temperatures of the semiconductor package 12 and the display housing17 are over the predetermined value, the processing proceeds to step S8.In step S8, processing speed of the semiconductor package 12 is reducedtemporarily so as to reduce power consumption of the semiconductorpackage 12 thereby suppressing generation of heat in the IC chip 14.

[0103] According to such a portable computer 1, cooling medium is forcedto circulate between the heat receiving head 31 and the heat radiator 32so as to transfer heat of the semiconductor package 12 to the displayhousing 17 effectively and discharge it into the atmosphere. Therefore,as compared to the conventional ordinary forced air cooling system, heatradiation of the semiconductor package 12 can be raised thereby makingit possible to correspond to increase of generation of heat reasonably.

[0104] Further, according to the above-described structure, the coolingmedium heated by the heat receiving head 31 is cooled through theintermediate cooling unit 70 before it reaches the heat radiator 32.Thus, the temperature of the cooling medium fed to the heat radiator 32can be lowered so that a rise of the surface temperature of the displayhousing 17 receiving heat of the heat radiator 32 can be suppressed.Thus, if an operator touch the surface of the display housing 17 withhis hand when for example, adjusting the standing angle of the displayunit 3 or carrying the portable computer 1, he never feels a sudden ofheat, thereby making it possible to lower a thermal influence of theportable computer 1 upon the human body during use.

[0105] At the same time when the portable computer 1 is powered on,circulation of cooling medium is started so as to transfer heat of thesemiconductor package 12 to the heat radiator 32. Thus, at the time oflow/medium load in which the temperature of the semiconductor package 12is not raised so much, it is possible to stop operation of the electricfan 90 or suppress the rotation speed, thereby enabling a silentoperation.

[0106] Further, because the pump 76 and the accumulator 77 are built inthe main body 71 of the intermediate cooling unit 70, a structurecontaining a movable portion can be handled as a single unit. Thus,incorporation of the cooling unit 30 into the first housing 4 can befacilitated, thereby improving operation efficiency of assembly of theportable computer 1.

[0107] Additionally, the first pipe line 50 for introducing coolingmedium heated by the heat receiving head 31 to the heat radiator 32 andthe second pipe line 51 for returning cooling medium cooled by the heatradiator 32 to the heat receiving head 31 are disposed on the left andright leg portions 23 a and 23 b of the display housing 17. Thus, atportions where the first and second pipe lines 50 and 51 are stretchedbetween the first housing 4 and the display housing 17, these first andsecond pipe lines 50 and 51 can be kept apart from each other so as toseparate them thermally. Thus, it is possible to prevent an undesiredheat exchange between the first pipe line 50 and the second pipeline 51,thereby raising heat transfer efficiency from the heat receiving head 31to the heat radiator 32.

[0108] On the other hand, a procedure for removing the display unit 3from the first housing 4 in the portable computer 1 having theabove-described structure will be described.

[0109] First, as shown in FIG. 6, the display unit 3 is rotated to theclosing position, so that the screws 63 which fix the lids 61 areexposed rearward of the display supporting portions 10 a and 10 b. Next,the screws 63 are loosened so as to release fixing of the lids 61 withthese screws 63. After that, engagement between the fitting pawl 62 andthe heat radiator 32 is released and the lids 61 are removed from thedisplay housing 17. Consequently, as shown in FIG. 7, the openingportions 60 a and 60 b are opened so that the bellows pipes 52 insertedinside the leg portions 23 a and 23 b are exposed toward the rear face21 of the display housing 17 through the opening portions 60 a and 60 b.

[0110] Next, the screws 56 which fix the first and second heat radiatingplates 43 a and 43 b to the display housing 17 are loosened so as torelease engagement between the heat radiator 32 and the display housing17. Subsequently, the fitting pawls 55 a and 55 b of the heat radiator32 are separated from the opening edge portion of the mounting port 54and then, this heat radiator 32 is taken out in the direction of therear face 21 of the display housing 17 through the mounting port 54.This procedure for taking out this heat radiator 32 can be carried outirrespective of whether the display unit 3 is rotated to its closingposition or the opening position.

[0111] Because the opening portions 60 a and 60 b are continuous to themounting port 54, the first and second pipe lines 50 and 51 continuousto this heat radiator 32 are pulled out of the opening portions 60 a and60 b rearward of the leg portions 23 a and 23 b at the same time whenthe heat radiator 32 is taken out of the mounting port 54. Because atthis time, the second pipe line 51 is disposed behind the hinge shaft27, the hinge shaft 27 never becomes an obstacle when taking the secondpipe 51 out of the leg portion 23 a.

[0112] Thus, with the first and second pipe lines 50 and 51 connected tothe heat radiator 32 as shown in FIG. 13, the heat radiator 32 can bepulled out rearward of the display housing 17.

[0113] Next, by taking the top cover 6 of the first housing 4 out of thebase 5, the first bracket 25 of the hinge device 24 fixed to this base 5is exposed. Finally, the fixing between the first bracket 25 and theboss portion 28 with the screws is released and the display unit 3 istaken out upward of the base 5 together with the hinge device 24. Thus,the display unit 3 and the computer main body 2 can be separated fromeach other.

[0114] When mounting the display unit 3 onto the computer main body 2,the first bracket 25 of the hinge device 24 is screwed to the bossportion 28 of the base 5 before the top cover 6 is mounted on the base5. After that, the top cover 6 is mounted on the base 5 so as to coverthe first bracket 25 with this top cover 6.

[0115] Next, the heat radiator 32 is fitted with the mounting port 54 inthe rear face 21 of the display housing 17, so that the fitting pawls 55a and 55 b of the first heat radiating plate 43 a are hooked on theopening edge portion of the mounting port 54. Further, the lower edgeportions of the first and second heat radiating plates 43 a and 43 b arefixed to the display housing 17 with the screws 56. Subsequently, thefirst and second pipe lines 50 and 51 continuous to the heat radiator 32are inserted inside the leg portions 23 a and 23 b through the openingportions 60 a and 60 b.

[0116] Finally, the lids 61 are fitted with the opening portions 60 aand 60 b and these lids 61 are fixed to the leg portions 23 a and 23 bwith the screws 63. Consequently, the computer main body 2 and thedisplay unit 3 are coupled with each other rotatably, so that theincorporation of the heat radiator 32 in the display housing 17 iscompleted.

[0117] With such a structure, the heat radiator 32 accommodated in thedisplay housing 17 can be taken out of the rear face 21 of the displayhousing 17 together with the first and second pipe lines 50 and 51.Thus, with the heat radiator 32 taken out of the display housing 17, thedisplay unit 3 can be taken out of the first housing 4 or installed tothe first housing 4.

[0118] Therefore, when attaching/detaching the display unit 3 to/fromthe first housing 4, it is not necessary to release thermal connectionbetween the heat receiving head 31 and the semiconductor package 12 orthermally connect again, so that the procedure for disassembly/assemblyof the thermally connecting portion between the heat receiving head 31and the semiconductor package 12 is not required.

[0119] Thus, no unreasonable force is applied to the precisionsemiconductor package 12 or the positional relationship between thesemiconductor package 12 and the heat receiving head 31 is not changed,so that reliability of heat conduction can be maintained favorably.

[0120] Further, the bellows pipe 52 in the second pipe line 51 isdisposed behind the hinge shaft 27 inside the leg portion 23 a. Thus,the curvature of the bellows pipe 52 when the display unit 3 is rotatedto the closing position can be suppressed to be small as shown in FIG.5. As a result, when the display unit 3 is rotated, an unreasonablebending force is not applied to the bellows pipe 52 thereby improvingthe durability of the bellows pipe 52.

[0121] Meanwhile, according to the first embodiment, when thetemperature of the semiconductor package and the temperature of thedisplay housing reach their predetermined values, the electric fan isstarted. However, the present invention is not restricted to this. Forexample, it is permissible to adjust the air amount of the cooling airor the flow amount of the cooling medium according to a temperaturesignal outputted from the temperature sensor.

[0122] Further, the pump and accumulator do not always have to be builttogether with the intermediate cooling unit and the pump and accumulatormay be installed halfway of the second pipe line. Because with thisstructure, cooling medium cooled by the radiator is introduced to thepump and accumulator, thermal influence upon the pump and accumulatorcan be suppressed thereby improving the reliability of the operation.

[0123] The present invention is not restricted to the above-describedfirst embodiment. A second embodiment of the present invention shown inFIG. 14 will be described.

[0124] The second embodiment is different from the first embodiment inthat the lids 61 which cover the opening portions 60 a and 60 b in theleg portions 23 a and 23 b are connected to each other through aconnecting panel 100. Other basic structure of the portable computer 1is the same as the first embodiment.

[0125] The connecting panel 100 is an elongated plate extending in thewidth direction of the display housing 17. The connecting panel 100 isfitted detachably in an end portion adjacent the leg portions 23 a and23 b of the mounting port 54 of the display housing 17 and functions asa cover portion for covering this mounting port 54 partially. Thisconnecting panel 100 is located on the same plane as the rear face 21 ofthe display housing 17 and the protective layer 57 of the heat radiator32.

[0126]FIG. 15 shows a third embodiment of the present invention.

[0127] This third embodiment is a further development of the secondembodiment. According to the third embodiment, a connecting panel 110for connecting the lids 61 is large enough to cover the mounting port 54entirely. The connecting panel 110 is fit to the mounting port 54detachably such that it is overlaid on the first heat radiating plate 43a of the heat radiator 32 supported by the display housing 17. Thus, thefirst heat radiating plate 43 a of the heat radiator 32 is not equippedwith any protective layer like shown in the first embodiment and thisconnecting panel 110 functions a protective layer which covers the firstheat radiating plate 43 a.

[0128] Further, FIGS. 16-18 show a fourth embodiment of the presentinvention.

[0129] According to the fourth embodiment, the structure of a coolingunit 120 for cooling mainly the semiconductor package 12 is differentfrom that of the first embodiment and other basic structure of theportable computer 1 is the same as the first embodiment. Thus, for thefourth embodiment, like reference numerals are attached to the samecomponent as the first embodiment and a description thereof is omitted.

[0130] As shown in FIG. 16, the convex portion 8 located at the rear endportion of the first housing 4 is so constructed that both ends thereofare located inside in the width direction of the first housing 4 withrespect to the side wall 4 c of the first housing 4. At the rear endportion of the first housing 4 are formed a pair of display supportingportions 121 a and 121 b which are specified by both end faces of theconvex portion 8 and a top face of the upper wall 4 b.

[0131] The leg portions 23 a and 23 b of the display housing 17 areintroduced to the display supporting portions 121 a and 121 b. These legportions 23 a and 23 b have side faces opposing both end faces of theconvex portion 8.

[0132] The hinge shaft 27 of the hinge device 24 is extendedhorizontally such that it passes through the right end face of theconvex portion 8 and the right side face of the leg portion 23 a. Theleg portion 23 b located on the left opposite to the hinge device 24 hasa cylindrical guide 122 protruded from a side face thereof toward theleft end face of the convex portion 8. The guide 122 passes through theleft end face of the convex portion 8 rotatably such that it is openinside the convex portion 8. Thus, the inside of the first housing 4 andthe inside of the display housing 17 communicate with each other throughthe guide 122 and the left leg portion 23 b.

[0133] The cooling unit 120 for cooling the semiconductor package 12comprises a heat receiving head 31 accommodated inside the first housing4, a heat radiator 123 accommodated inside the display housing 17 and acirculating path 124 for connecting the heat receiving head 31 and theheat radiator 123.

[0134] The heat radiator 123 has a flat heat radiating plate 125 and ameanderingly bent heat radiating pipe 126. The heat radiating plate 125is composed of, for example, metallic material having excellent heatconductivity like aluminum alloy. The heat radiating plate 125 is fixedto an inside face of the display housing 17 behind the liquid crystaldisplay panel 18 with fixing means such as screws, adhesive agent andthe like, so that it is thermally connected to the display housing 17.

[0135] The heat radiating pipe 126 is composed of aluminum alloy orcopper base metallic material having an excellent heat conductivity. Theheat radiating pipe 126 is fixed to the heat radiating plate 125 bybonding or soldering means so that it is thermally connected to thisheat radiating plate 126. The heat radiating pipe 126 is equipped with arefrigerant intake 127 and a refrigerant outlet 128. The refrigerantintake 127 and the refrigerant outlet 128 are located at the left endportion of the heat radiator 123.

[0136] The circulating path 124 includes a first pipe line 130 and asecond pipe line 131. These pipe lines 130 and 131 are composed offlexible material like silicone resin, for example. The first pipe line130 is intended for connecting the refrigerant outlet 38 of the heatreceiving head 31 to the refrigerant intake 127 of the heat radiatingpipe 126. After introduced to the left end portion of the convex portion8 inside the first housing 4, this first pipe line 130 is introducedinto the display housing 17 through the guide 122 and the inside of theleg portion 23 b on the left. The second pipe line 131 is intended forconnecting the refrigerant outlet 128 of the heat radiating pipe 126 tothe refrigerant intake 37 of the heat receiving head 31. Afterintroduced to the left end portion of the convex portion 8 inside thefirst housing 4, the second pipe line 131 is introduced to the inside ofthe display housing 17 through the guide 122 and the leg portion 23 b onthe left side.

[0137] Thus, the refrigerant flow paths 36 of the heat receiving head 31is connected to the heat radiating pipe 126 of the heat radiator 123through the first and second pipe lines 130 and 131. The refrigerantflow paths 36, the heat radiating pipe 126 and the first/second pipelines 130 and 131 are filled with liquid-like cooling medium.

[0138] A pump 132 is installed halfway of the second pipe line 131. Whenthe power of the portable computer 1 is turned on, the pump 132 isstarted so as to send out cooling medium to the heat receiving head 31.As a result, the cooling medium is introduced to the heat radiator 123from the heat receiving head 31 through the first pipe line 130 andafter flowing through the heat radiating pipe 126 in this heat radiator132, returned to the pump 132 through the second pipe line 131.

[0139] As shown in FIG. 16, the first and second pipe lines 130 and 131have intermediate portions 133 a and 133 b. The intermediate portions133 a and 133 b exist between the convex portion 8 and the leg portion23 b of the display housing 17. The intermediate portions 133 a and 133b are extended horizontally along the axis X1 of the hinge shaft 27 suchthat they are disposed in parallel to each other with a gaptherebetween.

[0140] The intermediate portions 133 a and 133 b of the first and secondpipes 130 and 131 are provided with a holder 134 for keeping constantthe gap between these intermediate portions 133 a and 133 b. The holder134 is composed of material hard to transmit heat. As shown in FIG. 17,the holder 134 has a first support pipe 135 a and a second support pipe135 b. The first support pipe 135 a supports the intermediate portion133 a of the first pipe line 130 rotatably in an axial direction. Thesecond support pipe 135 b supports the intermediate portion 133 b of thesecond pipe line 131 rotatably in an axial direction.

[0141] The first and second support pipes 135 a and 135 b are linkedthrough a pair of columns 136. The columns 136 are extended in thediameter direction of the first and second support pipes 135 a and 135 bsuch that they are disposed between both end portions of these supportpipes 135 a and 135 b. Thus, the first and second support pipes 135 aand 135 b are disposed in parallel to each other across a heatinsulating gap 137.

[0142] As shown in FIG. 16, the first and second pipe lines 130 and 131are divided to upstream portions 130 a and 131 a and downstream portions130 b and 131 b inside the first housing 4. These upstream portions 130a and 131 a and the downstream portions 130 b and 131 b are joineddetachably through a joint 140. As shown in FIGS. 18A and 18B, the joint140 has a first joint portion 141 and a second joint portion 142. Thefirst joint portion 141 is connected to the downstream portion 130 b ofthe first pipe line 130 and the upstream portion 131 a of the secondpipe line 131. The second pipe portion 142 is connected to the upstreamportion 130 a of the first pipe line 130 and the downstream portion 131b of the second pipe line 131.

[0143] The first joint portion 141 has a hollow cylindrical body 145. Apair of refrigerant flow paths 146 are formed inside the body 145. Therefrigerant flow paths 146 are connected to the downstream portion 130 bof the first pipe line 130 and the upstream portion 131 a of the secondpipe line 131. Each of the refrigerant flow paths 146 has a valve hole147 which is open to an end of the body 145. A pair of pressing rods 148protruding from the body 145 through an opening edge portion of thevalve hole 147 are provided at a front end of the body 145.

[0144] A ball-like valve body 149 is accommodated in each refrigerantflow path 146 and used as a closing means. The valve body 149 issupported by the body 145 and can approach and leaves the valve hole147, always pressed toward the valve hole 147 by a spring 150. Thus,when the first joint portion 141 is separated from the second jointportion 142, the valve body 149 remains in firm contact with the openingedge portion of the valve hole 147, closing the valve hole 147.

[0145] The second joint portion 142 has a hollow cylindrical body 152. Apair of refrigerant flow paths 153 are formed inside the body 152. Therefrigerant flow paths 153 are connected to the upstream portion 130 aof the first pipe line 130 and the downstream portion 131 b of thesecond pipe line 131. Each of the refrigerant flow paths 153 has afitting hole 154, which is open to a front end of the body 152. The body145 of the first joint portion 141 removably secured to the fitting hole154 detachably.

[0146] As shown in FIG. 18B, a pressing protrusion 155 and a partitionwall 157 having a valve hole 156 are provided in the middle part of therefrigerant flow path 153. The protrusion 155 extends toward the fittinghole 154. The partition wall 157 opposes the fitting hole 154 across thepressing protrusion 155. A ball-like valve body 158 is accommodated as aclosing means between the partition wall 157 and the other end of therefrigerant flow path 153. The valve body 158 is supported by the body152 and can approach and leave the valve hole 156 and is always pressedtoward the valve hole 156 by a spring 159. Thus, while the first jointportion 141 is separated from the second joint portion 142, the valvebody 158 remains in firm contact with the opening edge portion of thevalve body 156, closing the valve hole 156.

[0147] When as shown in FIG. 18A, the body 145 of the first jointportion 141 is fit to the fitting holes 154 in the second joint portion142, the pressing protrusions 155 of the second joint portion 142 enterthe valve holes 147 in the first joint portion 141. The protrusions 155strike the valve bodies 149. Consequently, the valve bodies 149 arepushed and leave the opening edge portions of the valve holes 147, inspite of the force of the springs 150. The valve hole 147 are therebyopened.

[0148] At the same time, the pressing rods 148 of the body 145 passesover the periphery of the pressing protrusions 155 and enter the valveholes 156 in the joint portion 142. The rods 148 strike the valve bodies158. As a result, the valve bodies 158 are pushed and leave the openingedge portion of the valve holes 156, against the force of the springs159. The valve holes 156 are thereby opened.

[0149] Since the first joint portion 141 is connect with the secondjoint portion 142, the refrigerant flow paths 146 and 153 communicatewith each other through the valve holes 147 and 156.

[0150] When the first joint portion 141 is separated from the secondjoint portion 142 as shown in FIG. 18B, the valve bodies 149 are nolonger pressed by the pressing protrusions 155. At the same time, thevalve bodies 158 are no longer pressed by the pressing rods 148. Thus,the valve bodies 149 and 158 are pressed against the opening edgeportions of the valve holes 147 and 156 by the springs 150 and 159. Thebodies 149 and 158 seal the valve holes 147 and 156. Thus, therefrigerant flow paths 146 and 153 continuous to the first and secondpipe lines 130 and 131 are automatically closed, thereby preventing aleakage of the cooling medium.

[0151] If the IC chip 14 of the semiconductor package 12 is heated inthe portable computer 1 having such a structure, heat of the IC chip 14is transmitted to the heat transmitting case 34 of the heat receivinghead 31. Because the cooling medium is supplied to the refrigerant flowpaths 36 of this heat transmitting case 34, heat transmitted to the heattransmitting case 34 is transferred to the cooling medium flowingthrough the refrigerant flow paths 36 from the heat transmitting case34. After heated by heat exchange by means of this heat receiving head31, the cooling medium is introduced to the heat radiator 123 of thedisplay unit 3 through the first pipe line 130, so that heat of the ICchip 14 is transferred to the heat radiator 123 through a flow of thecooling medium.

[0152] The cooling medium introduced to the heat radiator 123 flowsalong the meandering heat radiating pipe 126. In this flow process, heatabsorbed in the cooling medium is transmitted to the heat radiating pipe126 and diffused by heat conductivity to the heat radiating plate 125.Because the heat radiating plate 125 is thermally connected to thedisplay housing 17, heat transferred to the heat radiating plate 125 isdiffused by heat conductivity to the display housing 17 and then,discharged into the atmosphere from the surface of the display housing17.

[0153] The cooling medium cooled by heat exchange by means of the heatradiating pipe 126 is returned to the pump 132 through the second pipeline 131 and after pressurized by this pump 132, supplied to the heatreceiving head 31.

[0154] The first pipe line 130 in which the cooling medium heated byheat exchange by means of the heat receiving head 31 flows and thesecond pipe line 131 in which the cooling medium cooled by heat exchangeby means of the heat radiator 123 extend between the first housing 4 andthe display housing 17. Then, the intermediate portion 133 a of thefirst pipe line 130 and the intermediate portion 133 b of the secondpipe line 131 are held by the first and second support pipes 135 a and135 b in the holder 134. Consequently, the gap between the first pipeline 130 and the second pipe line 131 is maintained constant and the gapbetween the first pipe line 130 and the second pipe line 131 isthermally shut down by the gap 137 between the first and second supportpipe lines 135 a and 135 b.

[0155] Thus, although the first pipe line 130 in which the heatedcooling medium flows and the second pipe line 131 in which the cooledcooling medium flows pass inside the guide 122 such that they adjoineach other, a undesired heat exchange between the adjacent pipe lines130 and 131 can be prevented. Therefore, transmission efficiency of heatfrom the heat receiving head 31 to the heat radiator 123 can be raised,thereby maintaining heat radiation performance of the semiconductorpackage 12.

[0156] On the other hand, a procedure for taking the display unit 3 outof the first housing 4 in the portable computer 1 having such astructure will be described. First, the top cover 6 of the first housing4 is removed from the base 5 so as to expose the first and second pipelines 130 and 131 and the joint 140 accommodated in the first housing 4.

[0157] Next, the first joint portion 141 and the second joint portion142 of the joint 140 are separated from each other and the first andsecond pipe lines 130 and 131 are divided to the upstream portions 130 aand 131 a and the downstream portions 130 b and 131 b inside the firsthousing 4. Consequently, the circulating path 124 is divided between thefirst housing 4 and the display unit 3. Thus, with the heat receivinghead 31 remaining in the first housing 4, the display unit 3 can beremoved from the first housing 4 or can be installed onto the firsthousing 4.

[0158] For the reason, when attaching or detaching the display unit 3to/from the first housing 4, it is not necessary to release thermalconnection between the heat receiving head 31 and the semiconductorpackage 12 or thermally connect again, so that the procedure fordisassembly/assembly of the thermal connecting portion between the heatreceiving head 31 and the semiconductor package 12 is not required.Therefore, no unreasonable force is applied to the precisionsemiconductor package 12 and the positional relationship between thesemiconductor package 12 and the heat receiving head 31 is not changed,thereby maintaining reliability of heat transfer favorably.

[0159] Further, if the first joint portion 141 is separated from thesecond joint portion 142, the valve holes 147 and 156 in the respectivejoint portions 141 and 142 are automatically shut down by the valvebodies 149, 158. Thus, a leakage of the cooling medium can be preventedand any special procedure for sealing a dividing portion between thefirst and second pipe lines 130 and 131 is not required.

[0160] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A cooling unit for use in an electronic apparatushaving a computer main body containing a heat generating component and adisplay unit supported by said computer main body, said cooling unitcomprising: a heat receiving portion thermally connected to said heatgenerating component and accommodated in said computer main body; a heatexchanging portion installed on said display unit; circulating means forcirculating cooling medium between said heat receiving portion and saidheat exchanging portion, said circulating means having a pipe line forintroducing cooling medium heated by said heat receiving portion to saidheat exchanging portion; and intermediate cooling means installed insaid pipe line, said intermediate cooling means forcing the heatedcooling medium flowing from said heat receiving portion to said heatexchanging portion to be cooled.
 2. A cooling unit according to claim 1,wherein said intermediate cooling means comprises a main body having apath in which the heated cooling medium flows and a fan for supplyingcooling air to said main body.
 3. A cooling unit according to claim 2,wherein said main body comprises a cooling air path in which saidcooling air flows and a plurality of heat radiating fins exposed on saidcooling air path, said cooling air path being thermally connected tosaid path.
 4. A cooling unit according to claim 2, wherein saidcirculating means includes a pump for forcing the cooling medium to becirculated between said heat receiving portion and said heat exchangingportion and an accumulator for absorbing a pulsation of the coolingmedium discharged from said pump.
 5. A cooling unit according to claim4, wherein said pump and said accumulator are incorporated in said mainbody integrally.
 6. An electronic apparatus comprising: a housingcontaining a heat generating component; a display unit supported by saidhousing; a heat receiving portion accommodated in said housing andthermally connected to said heat generating component; a heat exchangingportion installed on said display unit; circulating means forcirculating cooling medium between said heat receiving portion and saidheat exchanging portion, said circulating means being disposedthroughout said housing and said display unit and having a pipe line forintroducing cooling medium heated by said heat receiving portion to saidheat exchanging portion; and intermediate cooling means installed insaid pipe line of said circulating means, said intermediate coolingmeans forcing the heated cooling medium flowing from said heat receivingportion to said heat exchanging portion to be cooled.
 7. An electronicapparatus according to claim 6, wherein said display unit contains adisplay housing incorporating the display panel, said heat exchangingportion has thermally conductive heat radiating plates supported by saiddisplay housing, said heat radiating plates being provided with heatradiating path for introducing the heated cooling medium.
 8. Anelectronic apparatus according to claim 6, wherein said circulatingmeans includes a pump for forcing said cooling medium to be circulatedbetween said heat receiving portion and said heat exchanging portion andsaid intermediate cooling means contains a main body having a path inwhich the heated cooling medium flows and a fan for supplying coolingair to said main body.
 9. An electronic apparatus according to claim 8,wherein the pump of said circulating means is driven when the power ofsaid electronic apparatus is turned on and said fan is driven when thetemperature of said heat generating component reaches a predeterminedvalue.
 10. An electronic apparatus according to claim 9, wherein saidfan is driven when the temperature of said display unit reaches apredetermined value.
 11. An electronic apparatus comprising: a firsthousing containing a heat generating component; a second housing, saidsecond housing being journaled detachably on a rear end of said firsthousing through a hinge device having a hinge shaft extending in thewidth direction of said first housing and having a rear face which isdirected backward of said first housing when said second housing isrotated to a posture in which it stands up from the rear end of saidfirst housing; a heat receiving portion accommodated inside said firsthousing and thermally connected to said heat generating component; aheat exchanging portion installed on said second housing, said heatexchanging portion being capable of being taken out of said rear face;and circulating means for circulating the cooling medium between saidheat receiving portion and said heat exchanging portion, saidcirculating means comprising a first pipe line for introducing coolingmedium heated by said heat receiving portion to said heat exchangingportion and a second pipe line for introducing cooling medium cooled byheat exchange by means of said heat exchanging portion to said heatreceiving portion, said first and second pipe lines being disposedthroughout the inside of said first housing and the inside of saidsecond housing via backward of said hinge shaft, said rear face of saidsecond housing having at least an opening portion at a positioncorresponding to said first and second pipe lines, said opening portionbeing covered with a removable lid.
 12. An electronic apparatusaccording to claim 11, wherein at least a portion passing behind thehinge shaft, of each of said first and second pipe lines hasflexibility.
 13. An electronic apparatus according to claim 11, whereinportions extending between said first housing and said second housing ofsaid first and second pipe lines are disposed apart from each other inthe width direction of the housings.
 14. An electronic apparatusaccording to claim 12, wherein said heat exchanging portion containsthermally conductive heat radiating plates having a heat radiating pathfor introducing the heated cooling medium and said second housingcontains a mounting hole in which said heat radiating plates are to beembedded in a rear face thereof, said mounting hole being continuous tosaid opening portions.
 15. An electronic apparatus according to claim14, wherein a face on an opposite side to said heat radiating path, ofsaid-heat radiating plate is covered with a protective layer having alower heat conductivity than the heat radiating plate and saidprotective layer is exposed out of said second housing through saidmounting hole.
 16. An electronic apparatus according to claim 14,wherein said lid is provided integrally with a cover portion forcovering said heat radiating plate, said cover portion being fit in saidmounting hole detachably.
 17. An electronic apparatus according to claim11, further comprising intermediate cooling means installed halfway ofsaid first pipe line, said intermediate cooling means forcing heatedcooling medium flowing from said heat receiving portion to said heatexchanging portion to be cooled.
 18. An electronic apparatus comprising:a housing accommodating a heat generating component and being capable ofbeing opened upward; a display unit supported by said housing; a heatreceiving portion accommodated in said housing and thermally connectedto said heat generating component; a heat exchanging portion installedon said display unit; and circulating means for circulating coolingmedium between said heat receiving portion and said heat exchangingportion, said circulating means comprising a first pipe line forintroducing cooling medium heated by said heat receiving portion to saidheat exchanging portion and a second pipe line for introducing coolingmedium cooled by heat exchange by means of said heat exchanging portionto said heat receiving portion, said first and second pipe lines beingdisposed throughout the inside of said housing and the inside of saiddisplay unit and being divided to upstream portions and downstreamportions inside said housing, said upstream portions and said downstreamportions being connected detachably through a joint, said joint havingclosing means for closing said first and second pipe lines when saidfirst and second pipe lines are divided to the upstream portions and thedownstream portions.
 19. An electronic apparatus according to claim 18,wherein said display unit has a pair of leg portions disposed apart fromeach other in the width direction thereof, said leg portions beingsupported rotatably by said housing.
 20. An electronic apparatusaccording to claim 19, wherein said first and second pipe lines areplaced through the inside of at least any one of said leg portions andthermally insulated from each other inside said leg portions.